Bio-based liner mat for waste pit

Abstract

A liner mat for waste pit management and drilling fluid recycling at well sites is described. The liner mat includes an adsorbent layer and a base layer. The adsorbent layer includes chitosan and polyhydroxyalkanoate (PHA). The base layer includes polylactic acid (PLA). In some cases, the base layer includes hydroxyapatite (HAp). The adsorbent layer contacts the drilling fluid. The adsorbent layer can mitigate microbial growth and adsorbs at least a portion of pollutants from the drilling fluid. The base layer provides structural support and resistance against mechanical stress and tearing.

What is claimed is: 
     
         1 . A method comprising:
 contacting, with a liner mat disposed in a waste pit, a drilling fluid that has flowed through a wellbore formed in a subterranean formation, wherein the drilling fluid comprises metal ions and pollutants, wherein the liner mat comprises:
 a adsorbent layer comprising chitosan and a polyhydroxyalkanoate (PHA), wherein a chitosan content of the adsorbent layer is greater than a PHA content of the adsorbent layer; and 
 a base layer comprising polylactic acid (PLA) and hydroxyapatite (HAp), wherein the base layer is in contact with the waste pit, wherein the base layer is configured to provide structural support and resistance against mechanical stress to the liner mat; 
   binding, by the adsorbent layer of the liner mat, at least a portion of the metal ions of the drilling fluid in response to contacting the drilling fluid to the liner mat, thereby removing at least the portion of the metal ions from the drilling fluid; and   adsorbing, by the adsorbent layer of the liner mat, at least a portion of the pollutants of the drilling fluid in response to contacting the drilling fluid to the liner mat, thereby removing at least the portion of the pollutants from the drilling fluid, wherein binding at least the portion of the metal ions and adsorbing at least the portion of the pollutants produces a treated drilling fluid, wherein the treated drilling fluid has a decreased content of metal ions and pollutants in comparison to the drilling fluid due to at least the portion of the metal ions and at least the portion of the pollutants remaining bound to the adsorbent layer of the liner mat.   
     
     
         2 . The method of  claim 1 , further comprising:
 separating the treated drilling fluid from the liner mat; and   reutilizing the treated drilling fluid from the waste pit for a cementing operation.   
     
     
         3 . The method of  claim 1 , further comprising, after separating the treated drilling fluid from the liner mat, rinsing the liner mat to unbind the metal ions from the liner mat and desorb the pollutants from the liner mat. 
     
     
         4 . The method of  claim 3 , further comprising:
 visually monitoring a physical condition of the liner mat; and   determining whether the liner mat is ready to be rinsed based on visually monitoring the physical condition of the liner mat.   
     
     
         5 . The method of  claim 1 , wherein the drilling fluid is contacted to the liner mat for a time duration in a range of from about 30 minutes to about 10 hours. 
     
     
         6 . The method of  claim 1 , wherein the adsorbent layer contacts the drilling fluid, and the base layer contacts a surface of the waste pit. 
     
     
         7 . The method of  claim 1 , wherein the PHA comprises at least one of trimethylbutyrate, hydrogen peroxide, 3-hydroxyhexanoate, oxygenated octanoate, 4-hydroxybutyrate, hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxy-2-methylbutyrate, 3-hydroxy-2-methylvalerate, or 3-hydroxypropionate as a monomer of the PHA. 
     
     
         8 . The method of  claim 7 , wherein the PHA is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). 
     
     
         9 . The method of  claim 8 , wherein the adsorbent layer has a first thickness in a range of from about 0.5 millimeters (mm) to about 20 mm, and the base layer has a second thickness in a range of from about 0.1 mm to about 10 mm. 
     
     
         10 . A liner mat for waste pit management and drilling fluid reutilization at well sites, the liner mat comprising:
 a adsorbent layer comprising chitosan and a polyhydroxyalkanoate (PHA), wherein a chitosan content of the adsorbent layer is greater than a PHA content of the first layer, wherein the adsorbent layer comprises a top surface configured to contact the drilling fluid, wherein the chitosan of the adsorbent layer is configured to mitigate microbial growth and adsorb at least a portion of pollutants from the drilling fluid, wherein the chitosan and the PHA of the adsorbent layer are configured to bind with at least a portion of metal ions of the drilling fluid which is in contact with the adsorbent layer, thereby removing the portion of metal ions from the drilling fluid; and   a base layer comprising polylactic acid (PLA) and hydroxyapatite (HAp), wherein the base layer is coupled to the adsorbent layer at an opposite side of the top surface of the adsorbent layer, wherein the base layer comprises a bottom surface configured to contact the waste pit, wherein the base layer is configured to provide structural support and resistance against mechanical stress to the liner mat.   
     
     
         11 . The liner mat of  claim 10 , wherein the PHA comprises at least one of trimethylbutyrate, hydrogen peroxide, 3-hydroxyhexanoate, oxygenated octanoate, 4-hydroxybutyrate, hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxy-2-methylbutyrate, 3-hydroxy-2-methylvalerate, or 3-hydroxypropionate as a monomer of the PHA. 
     
     
         12 . The liner mat of  claim 11 , wherein the PHA is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). 
     
     
         13 . The liner mat of  claim 12 , wherein the polylactic acid has an average molecular weight of about 1.6×10 5  Daltons. 
     
     
         14 . The liner mat of  claim 13 , wherein a first thickness of the adsorbent layer is in a range of from about 0.5 millimeters (mm) to about 20 mm, and a second thickness of the base layer is in a range of from about 0.1 mm to about 10 mm. 
     
     
         15 . A wellbore drilling system comprising:
 a waste pit located at a well site;   a circulation system at the well site, the circulation system comprising:
 a fluid pump configured to circulate a drilling fluid through a drill string assembly configured to drill into a subterranean formation to form a wellbore; and 
 a tubular configured to receive the drilling fluid that has been used to form the wellbore and direct the drilling fluid to a liner mat disposed in the waste pit, wherein the drilling fluid comprises metals and metal ions; and 
   the liner mat comprising:
 a adsorbent layer comprising chitosan and a polyhydroxyalkanoate (PHA), wherein a chitosan content of the adsorbent layer is greater than a PHA content of the adsorbent layer, wherein the adsorbent layer comprises a top surface configured to receive and contact the drilling fluid, wherein the chitosan of the adsorbent layer is configured to mitigate microbial growth and adsorb at least a portion of pollutants from the drilling fluid, wherein the chitosan and the PHA of the adsorbent layer are configured to bind with at least a portion of the metals and the metal ions from the drilling fluid which is in contact with the adsorbent layer, thereby removing at least the portion of the metals and the metal ions from the drilling fluid; and 
 a base layer comprising polylactic acid (PLA) and hydroxyapatite (HAp), wherein the base layer is coupled to the adsorbent layer at an opposite side of the top surface of the adsorbent layer, wherein the base layer comprises a bottom surface configured to contact the waste pit, wherein the base layer is configured to provide structural support and resistance against mechanical stress to the liner mat. 
   
     
     
         16 . The system of  claim 15 , further comprising a second tubular configured to direct flow of the drilling fluid from the waste pit back into the wellbore, wherein the drilling fluid flowing through the second tubular is substantially free of metals and metal ions due to the metals and metal ions remaining bound to the adsorbent layer of the liner mat. 
     
     
         17 . The system of  claim 15 , wherein the PHA comprises at least one of trimethylbutyrate, hydrogen peroxide, 3-hydroxyhexanoate, oxygenated octanoate, 4-hydroxybutyrate, hydroxydecanoate, 3-hydroxydodecanoate, 3-hydroxy-2-methylbutyrate, 3-hydroxy-2-methylvalerate, or 3-hydroxypropionate as a monomer of the PHA. 
     
     
         18 . The system of  claim 17 , wherein the PHA is selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). 
     
     
         19 . The system of  claim 15 , wherein the polylactic acid has an average molecular weight in a range of from about 1.5×10 5  Daltons to about 1.7×10 5  Daltons. 
     
     
         20 . The system of  claim 15 , wherein a first thickness of the adsorbent layer is in a range of from about 0.5 millimeters (mm) to about 20 mm, and a second thickness of the base layer is in a range of from about 0.1 mm to about 10 mm.